1. Field of the Invention
The present invention relates to a connector block for effecting an electrical connection between injectors (fuel injecting instrument) for a fuel injection device for an internal combustion engine for an automotive vehicle or the like through which fuel is injected and a power source for operating the injectors, and also relates to an improved receptacle junction terminal adapted to be accommodated in a terminal accommodating chamber of the connector block for relaying electricity by receiving therein tab-like male terminals from the respective ends thereof.
2. Statement of the Prior Art
An electrical connection between injectors for an internal combustion engine for an automotive vehicles or the like and a power source for operating those injectors is effected through a wiring system in which a main wire harness is laid out close to a fuel injection device having a multiplicity of injectors arranged herein, in which the main wire harness and the individual injectors are connected each other via groups of branched electrical wires connected to double-ended connectors, and in which the heat resistance of the groups of electrical wires are attained by covering each group of electrical wires with a heat-resistant tube.
However, this type of conventional electricity connecting structure has the following drawbacks:
(i) since connectors and electrical wires are subjected to a high-temperature atmosphere and strong vibrations, the above connecting structure cannot meet the standard of resistance to vibrations and heat required for such an application, and therefore disconnection or heat deterioration cannot be avoided, resulting in poor reliability in quality in relation to resistance to vibrations and haet;
(ii) since individual injectors are connected to a main wire harness via individual branched wires, the number of components required for effecting an electrical connection has to be increased, resulting in an increase of manufacturing costs, and moreover, a complicated connecting operation is required, and this often causes electricity-connecting errors due to a mistake of simply forgetting to connect wires at connectors and/or deformation and/or breakage of connectors and so forth;
(iii) since not only a special consideration needs to be taken for the lay-out of wires but also the wires need to be covered with heat-resistant tubes with a view to eliminating as much as possible a risk of wires being broken or heat-deteriorated, no good efficiency in molding and laying out groups of wires cannot be expected; and
(iv) good visual configuration of laid-out wires cannot be expected, and therefore superior functional beauty of a wiring cannot be expected.
In addition, other examples of conventional receptacle junction terminals of this type for use with a connector block for injectors for an internal combustion engine are shown in FIGS. 5 and 6. FIG. 5 is a side view of one of the examples in which the basic structure of a junction terminal 203 is shown. FIG. 6(A) is a side view of a conventional junction terminal 303 of another type, and FIG. 6(B) is an exploded perspective view of FIG. 6(A).
According to its basic structure, the receptacle junction terminal 203 shown in FIG. 5 is inserted into a terminal accommodating chamber 11 of a connector block 1 so as to be accommodated therein, and receives, for example, a tab terminal 205A on the side of a connector and a tab terminal 205B on the side of an instrument from the respective ends thereof so that the terminals are securely inserted into contact sections 206 formed at the respective ends thereof for effecting an electrical connection. However, since this junction terminal 203 is inserted and accommodated in the terminal accommodating chamber 11 without any "play", when the tab terminal 205B on the side of an instrument is inserted into the junction terminal 203 accommodated in the terminal accommodating chamber 11 from the outside of the connector block 1 with a deviation E being present due to the deviation of the thickness-wise center line 219 of the tab terminal 205B relative to the center line 207 of the contact section 206 along which the tab terminal 205B is inserted, the resistance to the tab terminal 205B being inserted increases, resulting in poor workability. If the tab terminal 205B continues to be forcibly inserted irrespective of the resistance, the contact section 206 is then plastically deformed, and this causes a problem in which the electricity connecting performance of the junction terminal decreases.
The junction terminal shown in FIGS. 6(A), 6(B) is disclosed in U.S. Pat. No. 4,453,792 and was devised to solve the above problem. As shown in the drawings, this junction terminal of the U.S. patent comprises a pair of blade members 320A, 320B that are overlapped each other to form a contact section and a pair of spring members 321A, 321B that are placed on the left- and right-hand side edges of the pair of overlapped blade members 320A, 320B in such a manner as to hold the blade members from both sides. Thus, these four members are assembled to a receptacle junction terminal 303, and the receptacle junction terminal so assembled is accommodated in a terminal accommodating chamber 11 in such a manner that the elastic displacement thereof is allowed. In this construction, even if the center of the tab terminals 305 received in the receptacle junction terminal from the respective ends thereof deviates from the corresponding contact sections 306, the elastic displacement of the spring members 321A, 321B facilitates the insertion of the tab terminals 306.
Although this junction terminal according to the U.S. patent is superior in securely inserting the tab terminals 305 into the contact sections 306, it has the following drawbacks that affect its utility:
since it comprises four members, the number of components increases, and assembly work is needed, resulting in increase in manufacturing costs;
the structure is complicated, resulting in poor workability; and
the terminal accommodating chamber needs to be made such that the ends thereof are closed in order to stabilize the posture of the junction terminal when accommodated in the terminal accommodating chamber, a special locking means being thus required.